Changes In Water Quality Research Articles

Investigating the Impact of Wildfires on Lake Water Quality Using Earth Observation Satellites

A study was carried out to investigate the effects of wildfires on lake water quality using a source dataset of 2024 lakes worldwide, covering different lake types and ecological settings. Satellite-derived datasets (Lakes_cci and Fire_cci) were used and a Source Pathway Receptor approach applied which was conceptually represented by fires (burned area) as a source, precipitation/drought representing transport dynamics, and lakes as the ultimate receptor. This identified 106 lakes worldwide that are likely prone to be impacted by wildfires via a terrestrial pathway. Satellite-derived chlorophyll-a (Chl-a) and turbidity variables were used as indicators to detect changes in lake water quality potentially induced by wildfires over a four-year period. The lakes with the largest catchment areas burned and characterized by regular annual fires were located in Africa. Evidence for a strong influence of wildfires was not found across the dataset examined, although clearer responses were seen for some individual lakes. However, among the hydro-morphological characteristics examined, lake depth was found to be significant in determining Chl-a concentration peaks which were higher in shallow and lower in deep lakes. Lake turbidity responses indicated a dependence on lake catchment and weather conditions. While wildfires are likely to contribute to the nutrient load of lakes as found in previous studies, it is possible that in many cases it is not a dominant pressure and that its manifestation as a signal in lake Chl-a or turbidity values depends to a large part on lake typology and catchment characteristics. Assessment of lake water quality changes six months after a fire showed that Chl-a concentrations either increased, decreased, or showed no changes in a similar number of lakes, indicating that a lake specific ecological and hydro-morphological context is important for understanding lake responses to wildfires.

Effects of Acacia invasion on water quality, litterfall, aquatic decomposers, and leaf litter decomposition in streams

Abstract Small streams and their riparian vegetation are closely linked ecosystems. Thus, the invasion of native riparian forests with non‐native species can impact stream ecosystems. We assessed the effects of the invasion of broadleaf deciduous forests by evergreen, nitrogen‐fixing Acacia species on seasonal variation of relevant instream environmental variables, litterfall in the riparian area, aquatic decomposers, and leaf litter decomposition, by comparing three streams flowing through native forests (native streams) and three streams flowing through invaded forests (invaded streams) in central Portugal. Invaded streams flow through forests composed (almost) of monospecific stands of Acacia trees. Litterfall in the riparian area was sampled with fabric traps and sorted into five categories: leaf (including phyllodes), flower, fruit and seed, wood litter, and other materials. Aquatic hyphomycete conidia suspended in water were sampled to assess conidia concentration and community composition. Leaf litter of Quercus robur was enclosed in coarse‐mesh bags and incubated in streams to assess decomposition rates and associated macroinvertebrate density and community composition. Samples from each variable were collected monthly from streams over 1 year. Aquatic hyphomycete conidia concentration was higher in invaded streams in spring/summer when litter inputs, water temperature, and aquatic nutrient concentrations were higher. In contrast, conidia concentration was lower in invaded streams in autumn/winter as they received less native deciduous leaf litter in autumn than native streams. Aquatic hyphomycete community structure changed, and species richness was lower in invaded streams because aquatic nutrient concentrations were higher and leaf litter species richness was lower. Macroinvertebrate and shredder density in decomposing leaf litter did not differ between native and invaded streams, but litter bags may have artificially increased densities by providing high quality food and/or refuges in streams with poor‐quality resources. Nevertheless, macroinvertebrate community structure changed, and family richness was lower in invaded streams. Finally, decomposition rates of Q. robur leaf litter in coarse‐mesh bags were similar between stream types, despite differences in aquatic decomposer communities. Overall, Acacia invasion changed water quality, litterfall seasonality and composition, and aquatic decomposer communities (especially aquatic hyphomycetes). However, Acacia effects on macroinvertebrate density and leaf litter decomposition rates were less pronounced, suggesting that higher trophic levels may be more resilient to invasion than basal levels, or the invasion time/extent in our invaded streams was not strong enough to affect macroinvertebrates and associated processes. Instream invasion effects on aquatic hyphomycete communities were more strongly mediated by changes in litter inputs rather than increases in aquatic nutrient concentrations because they remained oligotrophic in invaded streams. Simplification of riparian and aquatic communities may render them less efficient in coping with additional environmental changes. Acacia effects might be mitigated by the maintenance of a riparian corridor composed of native vegetation. The protection of non‐invaded riparian galleries and restoration of invaded ones could protect and restore stream ecosystems.

Impacts of land use changes on discharge and water quality in rivers and streams: Case study of the continental United States

AbstractWater quality trends in streams and rivers are impacted by several factors including land use of the watershed; however, it is unclear what influence changes in the land use of a watershed subsequently have on changes in discharge and water quality in streams and rivers. This study seeks to fill this gap by evaluating the relationship between changes in land use and changes in discharge and water quality at United States Geological Survey (USGS) stream gages over the period of 2008–2016. Using land cover data and discharge and water quality data from 60 USGS gages, regression methods were applied to determine the strength of relationship between land use changes and changes in water quality and quantity. Trends in discharge and water quality were mixed, with a majority of watersheds demonstrating a decrease in dissolved oxygen and turbidity, no overall trend for discharge, and increases in specific conductance. A regression analysis revealed that discharge, turbidity, and specific conductance were correlated with changes in individual land use types with an R2 between 0.12 and 0.25. Combining the influences of multiple land uses in multivariate regression improved the predictions for discharge (R2 0.58) and specific conductance (R2 0.47), highlighting the magnitude for which land cover changes influence trends in water quality. Overall, this study demonstrates the impact that large‐scale land use changes have on surface water quality.

Dry Me a River: Ecological Effects of Drought in the Upper San Francisco Estuary

Droughts have major effects on estuaries because freshwater entry is one of the defining features of an estuary, and freshwater flow is an important variable that determines the interannual change in the environment. In the upper San Francisco Estuary (the Sacramento–San Joaquin Delta, Suisun Bay, and Suisun Marsh), the Mediterranean climate includes frequent multi-year droughts. To assess ecosystem responses to droughts in the upper estuary, the Interagency Ecological Program Drought Synthesis Team assembled a set of flow, water quality, chlorophyll, zooplankton, and fish data from 1975 to 2021 to test for differences between multi-year droughts and multi-year wet periods and tested for linear relationships between each variable and the Sacramento Valley Hydrologic Index (see definitions and relationships as outlined in Appendix A). Our models showed droughts decreased Delta outflow, project exports, zooplankton in Suisun Bay, and some fish species. We also found that droughts increased water clarity, salinity, nutrients, chlorophyll in the South Delta, zooplankton in the South Delta, and water residence time. Although our analyses only tested correlations, we hypothesized that most of the food-web responses could be traced to increased residence time, decreased transport rates, or both. However, some responses may have been caused by secondary effects, including shifts in salinity gradients, regional changes in water quality, or differences in top-down effects of increased predation and grazing rates. With increased frequency of droughts in the future, this increasingly low-outflow, warming, clearing estuary—which is invaded by non-native species and has low pelagic fish production—is rapidly becoming the new “normal.”

Investigation of Water Quality of the Karasu River in Bilecik Province in terms of Agricultural Irrigation

Together with increasing people's need for water, water needs to be monitored due to the pressure created by factors such as drought and pollution. In this study, water quality was monitored by determining 10 points on the Karasu River in Bilecik Province and it was aimed to examine the seasonal change in water quality. pH, EC, Na, K, Ca, Mg, CO3, HCO3, Cl, B, SO4, Sodium Adsorption Rate (SAR), Residual Sodium Carbonate (RSC) and %Na parameters were determined in water. And then using these parameters, quality classes were determined with the help of water quality classification systems developed by scientists such as Schofield, Wilcox, Thorne, Doneen and Soifer. The study were temporally diveded into 4 periods. They are period 1, period 2 (Spring), period 3 (Summer) and period 4 (Fall). After all, for the period 3, heavy metal pollution, especially Al, attracts attention. Except for the period 2 of point 7 and period 4 of point 9, the class of all periods and points in terms of sulphate was "Very good (class 1)". According to Schofield (1933 and 1935) systems, point 7 is in particularly bad situation in terms of EC. According to Wilcox (1948), point 7 is not suitable for irrigation in the period 2. At point 7, water pollution in period 2 has been identified as common to most classification systems. According to Christiansen et al. (1977), there is intense pollution in terms of EC and Na2CO3 parameters. According to Soifer (1987), point 2 is the cleanest point. As a result, Karasu river is not suitable for irrigation in terms of Al and B. It was understood that heavy metal pollution did not cause much of a problem in non-industrialized cities such as Bilecik. Besides, it was understood that the most common element among heavy metals was Pb in Karasu River. The SAR and RSC values of all periods, seasons and points were classified as "Very Good-Safe (C1S1)".

The effect of water quality change on copper flotation

Given the significant consumption and future demand for water resources, this paper intends to find the conditions for using a flotation process with different water quality. One of the alternatives is using water under secondary treatment with industrial water mixtures to partly recycle domestic wastewater and maximize metallurgical benefits. Results show that using wastewater (only with secondary treatment) in flotation is detrimental to copper recovery. However, molybdenum recovery is significantly improved. For mixtures with 50 [%] wastewater, 50 [ppm] frother, 20 [ppm] collector, and pH 10, copper recovery decrease amounts to 0.4 [%], while molybdenum shows a 2.4 [%] recovery increase. In addition, copper concentrate grade decreases by 1.4 [%], while molybdenum grade remains. Therefore, using wastewater is viable, particularly in the case of molybdenum. So, this study proposes using of water mixtures in the copper depression stage to improve molybdenum recovery.

Hydrology Predominates Over Harvest History and Landscape Variation to Control Water Quality and Disinfection Byproduct Formation Potentials in Forested Pacific Coast Watersheds.

Despite the global importance of forested watersheds as sources of drinking water, few studies have examined the effects of forestry on drinking water treatability. Relatively little is known about how the interaction between landscape variation and flow impacts source water quality and what this interaction means for drinking water treatability. To address this knowledge gap, we examined variability in sediments, dissolved organic matter, and disinfection byproduct formation potentials (DBP-FPs) across a range of flow conditions in four small watersheds with contrasting forest harvest histories and soil characteristics on Vancouver Island. Storm event-driven change in streamflow was the primary driver of water quality and DBP-FPs at our sites, with greater changes during stormflow (e.g., a 3-fold increase in dissolved organic carbon concentrations) than those across contrasting watersheds. Flow-driven changes in water quality and DBP-FPs were not significantly different across watersheds with different harvest histories; muted responses may be attributed to widespread second growth forests (i.e., recent harvesting effects may be confounded by historical harvest), forestry practices (e.g., slash burning), or soils with low organic carbon storage. This study suggests that variation in hydrology predominates over harvest history and soil characteristics to drive water quality and DBP-FPs on the east coast of Vancouver Island.

Aquatic Insects (Ephemeroptera, Plecoptera and Trichoptera) Metric as an Important Tool in Water Quality Assessment in Hilly and Mountain Streams

The aim of the study was to test the significance of the EPT index in the water quality assessment of three types of water bodies in hilly and mountainous region of Serbia. The aquatic macroinvertebrate community was dominated by the group of insects, of which 95 taxa represent the EPT group. We compared the obtained values of biological indices used for the assessment of water quality according to the national legislation with the overall status assessment represented by the ecological quality classes (EQC). The results of the Spearman correlation test showed a negative correlation of EQC with the EPT index, BMWP score, H′, total number of taxa and number of sensitive taxa, while a positive correlation was observed for the values of SI and Tubificinae %. The values of EQC and biological indices were subjected to principal component analysis (PCA). The results showed that the parameters that contributed most to the differences were the EPT index, the BMWP score and the number of sensitive taxa. The results indicate that the EPT index is an excellent indicator of changes in water quality and an important tool for the ecological categorization of water bodies in mountain regions.

Effects of Land Use Types on Water Quality at Different Buffer Scales: Tianjin Section of the Haihe River Basin as an Example

It is important to explore the relationship between land use types and water quality to improve the surface water environment. Based on monthly water quality monitoring data from 16 nationally controlled surface water quality monitoring stations in Tianjin and land use data in 2021, GIS spatial analysis and mathematical and statistical methods were used to study the influence of land use types on surface water quality in buffer zones at different scales. The results showed that:① the land use types in the study area were mainly construction land, farmland, and water areas, which had significant effects on river water quality. Except for water temperature (WT) and pH, the farmland, construction land, and water areas were negatively correlated with each water quality indicator; forest land and grassland were positively correlated with dissolved oxygen (DO) and total nitrogen (TN) and negatively correlated with other water quality indicators. ② The water quality indicators showed obvious spatial differences in different seasons. The pH, DO and TN concentrations were higher in the dry season, whereas the permanganate index, ammonia nitrogen (NH4+-N), and total phosphorus (TP) concentrations were higher in the rainy season. ③ The results of the RDA analysis showed that the 800 m buffer zone land use had the greatest explanatory power for water quality changes in the dry season (50.4%), whereas the 3 000 m buffer zone land use could explain the water quality changes in the rainy season to the greatest extent (49.6%); from the average explanation rate of the dry and rainy seasons, the 3 000 m buffer zone was the best impact scale (50.0%) on water quality indicators in Tianjin. ④ The partial least squares regression (PLSR) analysis showed that the most important variables affecting surface water quality changes were construction land, farmland, and water areas. The predictive ability of the PLSR model of most water quality indicators was stronger in the dry season than that in the rainy season. In the dry season, all water quality indicators, except WT and pH, were most influenced by farmland. In the rainy season, construction land had the greatest influence on WT and NH4+-N concentrations, and the most important influencing factor for the remaining water quality indicators was still farmland. This study showed that the rational planning of land use types within 3 000 m of rivers or lakes was beneficial to improving the water quality of surface water.

Long-term changes in water quality downstream of three abandoned metal mines

Abandoned metal mines pollute rivers with both acidic and circumneutral metal-rich waters, sometimes from well-mapped mines, but often from long-abandoned adits with limited historical records. Changes in water quality over the monitored timescales were calculated for three mines across Wales (Nantymwyn, Parys Mountain and Frongoch), each abandoned since the early 20th century. Using all available spot sampling data provided by the environmental regulator, it was found that there was a sustained input of metals to the receiving watercourses with no or limited reduction in the concentrations from the mines without remediation, despite the passage of time and impacts of weathering. At Nantymwyn, comparison with five months’ sampling in 2019 showed no significant change (p > 0.05) in metal concentrations compared to the same months in 1985. Parys Mountain showed an increase in filtered zinc concentrations of 2 % between 2004 and 2020. At Frongoch, however, a substantial reduction in its environmental impact was observed after remediation, including a 90 % reduction in total lead concentrations. Realisation that the pollution from these sites does not reduce over the decades since abandonment should galvanize the resolve to understand the highest priority sites, and where possible remediate them.

Modeling the spatial distribution of numbers of coral reef fish species and community types in the Western Indian Ocean faunal province

Predicting and mapping coral reef diversity at moderate scales can assist spatial planning and prioritizing conservation activities. We made coarse-scale (6.25 km2) predictive models for numbers of coral reef fish species and community composition starting with a spatially complete database of 70 environmental variables available for 7039 mapped reef cells in the Western Indian Ocean. An ensemble model was created from a process of variable elimination and selectivity to make the best predictions irrespective of human influences. This best model was compared to models using preselected variables commonly used to evaluate climate change and human fishing and water quality influences. Many variables (~27) contributed to the best number of species and community composition models, but local variables of biomass, depth, and retention connectivity were dominant predictors. The key human-influenced variables included fish biomass and distance to human populations, with weaker associations with sediments and nutrients. Climate-influenced variables were generally weaker and included median sea surface temperature (SST) with contributions in declining order from SST kurtosis, bimodality, excess summer heat, SST skewness, SST rate of rise, and coral cover. Community composition variability was best explained by 2 dominant community richness axes of damselfishes-angelfishes and butterflyfishes-parrotfishes. Numbers of damselfish-angelfish species were ecologically separated by depth, and damselfishes declined with increasing depth, median temperature, cumulative excess heat, rate of temperature rise, and chronic temperature stresses. Species of butterflyfish-parrotfish separated by median temperature, and butterflyfish numbers declined with increasing temperature, chronic and acute temperature variability, and the rate of temperature rise. Several fish diversity hotspots were found in the East African Coastal Current Ecoregion centered in Tanzania, followed by Mayotte, southern Kenya, and northern Mozambique. If biomass can be maintained, the broad distributions of species combined with compensatory community responses should maintain high diversity and ecological resilience to climate change and other human stressors.

A novel method for multi-pollutant monitoring in water supply systems using chemical machine vision.

Drinking water is vital for human health and life, but detecting multiple contaminants in it is challenging. Traditional testing methods are both time-consuming and labor-intensive, lacking the ability to capture abrupt changes in water quality over brief intervals. This paper proposes a direct analysis and rapid detection method of three indicators of arsenic, cadmium, and selenium in complex drinking water systems by combining a novel long-path spectral imager with machine learning models. Our technique can obtain multiple parameters in about 1s. The experiment involved setting up samples from various drinking water backgrounds and mixed groups, totaling 9360 injections. A raw visible light source ranging from 380 to 780nm was utilized, uniformly dispersing light into the sample cell through a filter. The residual beam was captured by a high-definition camera, forming a distinctive spectrum. Three deep learning models-ResNet-50, SqueezeNet V1.1, and GoogLeNet Inception V1-were employed. Datasets were divided into training, validation, and test sets in a 6:2:2 ratio, and prediction performance across different datasets was assessed using the coefficient of determination and root mean square error. The experimental results show that a well-trained machine learning model can extract a lot of feature image information and quickly predict multi-dimensional drinking water indicators with almost no preprocessing. The model's prediction performance is stable under different background drinking water systems. The method is accurate, efficient, and real-time and can be widely used in actual water supply systems. This study can improve the efficiency of water quality monitoring and treatment in water supply systems, and the method's potential for environmental monitoring, food safety, industrial testing, and other fields can be further explored in the future.

Spatial and Temporal Variability in Water Quality and Phytoplankton Community Composition in Charleston Harbor

The Charleston Harbor estuary is a dynamic ecosystem draining three rivers that surround the rapidly urbanizing greater Charleston area. Projected climate change impacts include elevated sea surface temperature and local changes in water quality that will likely alter biogeochemical cycling as well as phytoplankton abundance and community composition. Partnering with the local non-profit organization Charleston Waterkeeper, surface water samples were collected from late April through October 2021 at 20 sites in the Charleston Harbor estuary system. Water quality parameters measured included sea surface temperature (SST), salinity, pH, dissolved inorganic carbon, chromophoric dissolved organic matter (CDOM), phytoplankton pigments and nitrate and phosphate concentrations. Relatively high (6—16 μM) nitrate values were observed throughout the year and the nitrate to phosphate (N:P) ratios were consistently elevated (50—200) relative to the Redfield ratio of 16. Analysis of variance indicated that the delivery of nitrate, phosphate, and CDOM into the estuary came from upriver of the Charleston Harbor. For instance, CDOM was significantly impacted by tidal stage (p < 0.05) and was negatively correlated with salinity at low salinity sites, but no correlation was observed at high salinity sites. Seasonal patterns in phytoplankton community abundance and composition were driven by changes in SST, as overall phytoplankton biomass increased with a community shift from diatoms during colder months to flagellated cells such as prasinophytes during the warmer summer months. Phytoplankton diversity was greatest during the early summer and lowest in October. This study provides a reference baseline for water quality parameters and phytoplankton community composition in an estuarine ecosystem that is changing rapidly due to dredging and climate change processes.

A comprehensive multivariate investigation of the water quality of Kallada River in Kerala, India

The Kallada River is a remarkable water resource in Kerala and reviving several villages through its glorifying journey. An investigation was directed to evaluate the spatial and temporal status of water quality in Kallada River, Kerala using multivariate statistical tools from February 2019 to January 2021. The status of fifteen environmental variables was detected by using standard methodology. The increased levels of conductivity, total dissolved solids, biochemical oxygen demand, hardness, alkalinity, calcium, and magnesium were detected during the post-monsoon (PoM) season and those parameters were tend to increase towards the downstream stations. Some other variables such as turbidity, dissolved oxygen, NO3−, SiO2, and PO43− were higher during the monsoon (MoN) season. Temperature, pH, and chemical oxygen demand were higher during the pre-monsoon (PrM) season. Furthermore, multivariate statistical tools like principal component analysis (PCA), agglomerative cluster analysis (AHC), and pearsons correlation were used to assess spatio-temporal changes in water quality to reveal pollution. Contrarily, the midstream stations such as K6, K10, and the entire downstream area (K11 to K15) of the Kallada River is under the threats of many anthropogenic activities such as sewage effluents, sand mining and agricultural runoff when compared to the entire upstream stations (K1 to K5), and three midstream stations (K7 to K9). The presence of various organic and inorganic pollutants begins from K6 and drastically rises at K11. Hence, efforts are required to prevent the contamination in the Kallada River.

Dynamic analysis of port water quality: insights from Zhanjiang Port, China

Abstract The management of port water quality is crucial to marine ecological balance and has been of great concern. In the present study, the water quality monitoring data in Zhanjiang Port from 2015 to 2022 were utilized to analyze the spatiotemporal characteristics and reveal the correlation between different parameters. The structural equation model has been applied to profile the dominant factors of water quality level. The results showed that the port water quality was generally worse in summer and better in winter. Variations in total phosphorus (TP), chemical oxygen demand (COD) and total nitrogen (TN) content directly led to water quality changes in Zhanjiang Port, where an increase in TP content resulted in a significant decrease in water quality level (path coefficient is 2.87). Permanganate index (CODMn) and ammonia nitrogen content indirectly affected the water quality level, while changes in pH and dissolved oxygen (DO) showed no impact. Ammonia nitrogen, pH and DO contents were significantly associated with TP. Human activities and industrial production were identified as the main sources of water quality pollution. The increasing trend of certain water quality parameters highlights the urgency of implementing timely measures to improve water quality conditions in Zhanjiang Bay, China.

Change in water quality in an Amazonian microbasin: ecological and human health implications.

The decline in the quality of water resources in the Amazon is very rapid in cities suffering from unplanned urban growth. The region has two defined seasons, winter (wet) and summer (dry), which directly affect the behavior of contaminants in aquatic ecosystems. The aim of this study was to assess the ecological and human health risks associated with the use of the watershed. In addition, an ecological index was proposed: the Quality Index for Aquatic Life, for the risk of contaminants to aquatic life. Sampling was carried out at six points in the Juá watershed. Physicochemical parameters, major anions, metals and total phosphorus were analyzed at both stations between 2020 and 2021. The highest concentrations of contaminants were found in the rainy season, due to the washing away of the banks. In this sense, Cl presented a concentration more than 307 times higher than that permitted by Brazilian legislation (wet). The ecological index showed that the watershed has a high risk of metals such as Cr III and Cr VI for the biota. The human health risk analysis showed a low risk; however, the lack of basic sanitation in the city indicates that monitoring of urban water resources is necessary.

Diatom metacommunity structuring in a large lake: geomorphic, water chemistry and dispersal effects on diatom guilds in Lake Ladoga (north-western Russia)

The relative importance of environmental filtering and dispersal in structuring metacommunities of littoral periphytic diatoms was assessed within a large lake (Lake Ladoga, north-western Russia). We hypothesized that different diatom functional guilds (high-profile, low-profile, motile and planktic) would respond differently to environmental and spatial variables, depending on their mode of attachment and dispersal ability. Guilds showed distinct distributional patterns along a gradient of wave-induced disturbance: low-profile diatoms dominated in exposed shorelines (high disturbance), whereas high-profile and motile diatoms were more abundant in coastal wetlands (low disturbance). Redundancy analysis with variation partitioning of the entire diatom community revealed that environmental variables (littoral geomorphology and water chemistry) outperformed spatial variables, indicating a predominant role of species sorting. When the diatom community was deconstructed into functional groups, benthic guilds (i.e., low-profile, high-profile and motile) showed higher dependence on environmental factors, whereas the planktic guild was primarily predicted by spatial factors. Thus, benthic taxa with lower dispersal abilities were less impacted by mass effects than planktic taxa. Among benthic guilds, motile diatoms were less sensitive to water chemistry compared to low-profile and high-profile diatoms, suggesting that a group-specific habitat preference may interfere with diatom responses to water quality changes. Hence, the response of diatom guilds to water quality parameters was related to their resistance to wave action. Overall, we concluded that the higher importance of environmental filtering than dispersal-related processes in shaping the diatom metacommunity resulted from a combination of a strong environmental gradient in geomorphology/water chemistry and the intermediate spatial scale of our study.

Hydrogeochemical characterization of the groundwater in northern and eastern areas of Kilwa district and Songosongo Island in, Tanzania

AbstractThis study aimed to investigate the hydrochemical and hydrogeochemical facies and mechanisms controlling groundwater quality from the northern and eastern parts of Kilwa district and Songosongo Island in Tanzania. Multifaceted methods were used to analyze the hydrochemical properties of water in relation to local geology and proximity to the Indian Ocean. The pH of the groundwater ranged from 5.18 to 7.56 with an average value of 6.64 which is slightly acidic. Electrical Conductivity (EC) ranged from 354 to 1429.50 μS/cm with an average value of 1652.6 μS/cm while Total Dissolved Solids (TDS) values varied from 170 to 1825 mg/L with an average value of 918.8 mg/L. The average values for Ca2+, Mg2+, Na+, and K+ were 36.9, 21.4, 152.5, and 13.31 mg/L, while for NO3−, Cl−, HCO3−, and SO42‐ were 2.1, 256.3, 156.6, and 45.8, respectively. The study found that groundwater closest to the ocean had elevated values of TDS, Na+, and Cl− and were more affected by seawater intrusion compared to those further inland. The dominant groundwater type was established to be Na‐Cl mostly nearest to the ocean while Ca‐Mg‐Cl was more encountered towards the inland. The groundwater in the northern and eastern parts of Kilwa is mainly controlled by seawater intrusion and recharge water. The Neogene formations consisting of clay, silts, coastal sands, and alluvium had lower Na+, Cl−, EC, and TDS values than the Paleogene which is more influenced by marine sediments. Thus, these findings call for improved groundwater monitoring to track changes in water quality since several parameters including sodium, magnesium, chlorides, TDS, EC, and pH were higher than recommended values for drinking purposes. However, the majority of the water samples were suitable for human consumption.

Impact of climate change on water quality evolution in cold regions using a water-heat-nitrogen processes coupled model.

Cold regions are particularly vulnerable to climate change. Thus, evaluating the response of water quality evolution to climate change in cold regions is vital for formulating adaptive countermeasures for pollution control under changing climatic conditions. Taking the Songhua River Basin (SRB) in Northeast China as the target area, we designed a water-heat-nitrogen coupled model based on the principle of water and energy transfer and nitrogen cycle processes model (WEP-N) in cold regions. The impact of climate change on pollution load and water quality was analyzed during the freezing, thawing, and non-freeze-thaw periods by taking the sudden change point (1998) of precipitation and runoff evolution in the SRB as the cut-off. The ammonia nitrogen load at Jiamusi station, the outlet control station in the SRB, was decreased by 1502.9 t in the change period (1999-2018) over the base period (1956-1998), with a - 9.2% decrease due to climate change. Compared to the ammonia nitrogen load during the base period, the ammonia nitrogen load decreased by - 171.3, - 506.9, and - 824.8 t during the freezing, thawing, and non-freeze-thaw periods, respectively, while the coefficient of variation showed an increasing trend during three periods, especially during the freezing and thawing periods. However, the water quality changes differed among periods owing to varying runoff during the year. Meanwhile, increasing runoff and decreasing ammonia nitrogen load improved water quality at Jiamusi station during the freezing period. During the thawing and non-freeze-thaw period, the water quality deteriorated due to the decrease in runoff more than the decrease in ammonia nitrogen load. Hence, the impact of climate change on water quality during thawing and non-freeze-thaw periods should be monitored to potentially offset the human influence on pollution control. The difference in the rate of change of the proportion of Class IV water between the two models with or without the soil freeze-thaw mechanism was 15.9%. The result shows that the application of a model that does not consider the freeze-thaw mechanism might slightly exaggerate the impact of climate change on water quality.

Experimental study on mine water purification mechanism for broken coal and rock masses in the underground reservoir of ecologically vulnerable mining area.

Water-rock interaction mechanism and water purification capacity of broken coal and rock masses are very important for the efficient operation of the underground reservoir. In this paper, a water purification simulation device for an underground mine reservoir was designed. The experimental study on the dynamic interaction between broken coal and rock masses and mine water was carried out. The water purification mechanism is analyzed from the changes in rock mineral composition and mine water quality before and after the test. The results show that after the broken coal and rock mass purification, the water turbidity and the concentration of chlorides and suspended solids decreased obviously. The water purification capacities of mudstone and sandstone are stronger than that of coal samples. After 60days of reaction between the working face sewage and the broken samples (mudstone, sandstone, and coal), the turbidity, chromaticity, and residual chlorine decreased by > 90%, 90%, and 60%, respectively; and COD decreased by 35.29%, 30.59%, and 28.99%, respectively. While the TDS and the total hardness increased by about 40%, 30%, and 10% for the mudstone, sandstone, and coal, respectively. It shows that coal also has the worst degradation performance. The water purification effect of broken coal and rock masses has a significant time effect. The early stage of water-rock interaction is dominated by mineral dissolution, and the middle stage is dominated by precipitation and adsorption. The pH value of the solution has a certain influence on the ion change. In the later stage, the water-rock interaction is weak in a dynamic equilibrium state, and the change in the mine water quality index is not obvious. Considering the influence of rock lithology on water quality and the law of water-rock interaction time, the construction site selection and water storage time optimization of underground reservoirs in Jinjie Coal Mine were carried out, respectively.